Up until now, there have been proposed a wide variety of conventional condenser microphones. One typical example of the conventional condenser microphone is disclosed in Japanese Patent Laid-Open Publication No. 2001-145196. The conventional condenser microphone disclosed therein comprises an electrically conductive capsule, an electrically conductive reinforcement plate having a circumferential ring portion at its circumferential end and disposed in the electrically conductive capsule, and an electrically conductive oscillation diaphragm spaced apart from the electrically conductive reinforcement plate and disposed in the electrically conductive capsule. The conventional condenser microphone is characterized in that the electrically conductive capsule and the electrically conductive reinforcement plate collectively form a cavity under the state that the circumferential ring portion of the electrically conductive reinforcement plate is held in engagement with the electrically conductive capsule. The conventional condenser microphone thus constructed is known as a condenser sensor.
In the conventional condenser microphone, the electrically conductive capsule has a relatively deformation-resistant portion in the form of a ring shape opposing to and to be held in engagement with the circumferential ring portion of the electrically conductive reinforcement plate so as to prevent the deformation of the electrically conductive capsule from being transmitted to the electrically conductive reinforcement plate.
Further, in the conventional condenser microphone, the deformation of the electrically conductive capsule is tolerated within the cavity formed by the electrically conductive capsule and the electrically conductive reinforcement plate so as to prevent the deformation of the electrically conductive capsule from being transmitted to the electrically conductive reinforcement plate.
The conventional condenser microphone thus constructed as previously mentioned, however, encounters a drawback that the frequency characteristics of the conventional condenser microphone tend to be aggravated resulting from the fact that the deformation of the electrically conductive capsule is tolerated, and the cavity in the electrically conductive capsule is deformed.
It is therefore an object of the present invention to provide a condenser sensor which can prevent the frequency characteristics from being aggravated.